This invention relates generally to connectors or the like and more particularly to an improved grounding connector for achieving a watertight connection between a jacketed, interlocked armored cable and a junction box or the like.
One example of the prior art in the general field to which the present invention is directed, is disclosed in U.S. Pat. No. 3,567,843 granted to K. M. Collins, et al. on Mar. 2, 1971. The Collins et al structure provides a body member having a first threaded portion that is adapted to be connected to a junction box, an internal conical bore and a second threaded portion that is arranged to receive a compression nut. A resilient grommet having a cylindrical bore that is approximately equal to the outside diameter of the cable and a conical outer surface that is complementary to the conical bore in the body member is inserted in the body member. A plurality of grounding stirrups are crimped to the grommet so that a portion thereof is in contact with the body member and simultaneously in contact with the metallic armor of the cable. While the Collins et al patent does disclose effective structure, is also exhibits several serious drawbacks. First of all there is the necessity of performing additional operations in order to crimp the stirrups to the grommet. Furthermore, the stirrups are internal and not visually accessible, should they be inadvertently omitted such error will not be perceived readily and will therefore be an absence of electrical grounding. Furthermore, the Collins et al patent relies on the compression force of the nut and, while this is usually effective, it is unpredictable. If the nut is not sufficiently tightened, the Collins et al structure will not provide efficient grounding.
Still another example of the prior art is disclosed in U.S. Pat. No. 2,816,949, granted on Dec. 17, 1957 to L. M. Curtiss. The Curtiss patent discloses an electric fitting for effecting a grounded, water tight connection between an outlet box and a metal jacketed cable connector. There is provided a tubular connector having externally threaded opposite end portions including a flange therebetween. The externally threaded portion is adapted to be secured in an opening in one wall of an outlet box by means of a lock nut that is threaded on one of the end portions. The opposite end portion of the tubular connector is provided with a counterbore that terminates in an inclined shoulder. A gland-nut is threaded on the opposite end portion of the tubular connector and is provided with an internal flange at its outer end that defines an annular shoulder presenting an opening substantially larger than the size of the cable. A resilient, rubber-like bushing having tapered opposite ends is seated at one end on the inclined shoulder and a spring metal disk of frusto-conical configuration in cross section and having a flange about its base end in the plane thereof is seated on the opposite end of the bushing with the flange being crimped between the bushing in the annular shoulder within the gland-nut whereby the bushing is shielded against exposure. A disk is provided centrally thereof with spaced openings formed on a radius corresponding substantially to that of the cable to define individual, aligned fingers that are integral with and in the plane thereof whereby when a cable is inserted through the disk and the bushing into the tubular connector, the cable is supported centrally of the tubular connector and the fingers are bent out of the plane of the disk into intimate contact with the cable to establish a ground connection through the outlet box.
The structure taught by the Curtiss patent, like the Collins et al structure is internal and is not readily visible to determine whether good electrical ground has been effected or whether or not the disk has, in fact, been put into place at all. In addition, the Curtiss structure also suffers the defect of having to rely on the compressive force of the gland-nut when it is threaded on the tubular connector in order to compress the bushing. Should the gland-nut become loose or should it not be tightened properly initially, it is quite likely that an ineffective ground connection will result.
Still another example of the prior art to which the present invention is directed is shown in U.S. Pat. No. 3,448,430, granted on June 3, 1969 to W. E. Kelly. In the Kelly Patent, there is disclosed a longitudinally split grounding ring having a plurality of outwardly angled fingers at one end thereof. The other end of the grounding ring is provided with a single piercing tooth that extends rearwardly or in a direction that is opposite to the direction of insertion of the cable. When a jacketed cable is used with the Kelly structure, the finger is inserted between the armor of the cable and the plastic jacket thereabout. The piercing tooth, in combination with the wall of the grounding ring is generally U-shaped and is arranged to receive between the legs thereof a resilient grommet with the juncture between the piercing tooth and the wall of the grounding ring serving as a stop for the plastic jacket of the cable and the grommet. In the assembled condition of the Kelly structure, the grommet is utilized for forcing the piercing tooth against the armor of the cable and to force the plurality of fingers against the connector body. As noted in the Kelly patent, the structure thereof may also be used without jacketing on the armored cable. In such a use, the piercing tooth is positioned within the bore of the grommet. However, the remaining structure and function is substantially the same as when the cable is jacketed.
It will be evident from a reading of the Kelly patent that effective grounding is achieved utilizing the compressive force of the grommet, a retaining ring and a gland-nut. It is particularly important to note that with the Kelly structure that grommet must exert a direct force on the ground ring in order to provide effective electrical grounding.